Presently, a face recognition system using a camera has been widely used. In an ordinary face recognition system, a passive image capture method is used. That is, the system only receives light but does not emit the light actively, or uses only a light supplement lamp to emit the light for the purpose of illumination only and without a structure. A face signal which is captured in this way is largely influenced by factors such as a change of ambient lighting, a change of a person's attitude or the like. When an angle of the face is changed, for example, when the face is turned to a side or is raised up, the image of the face will change largely, resulting in that the recognition becomes very difficult. When the ambient lighting is changed, for example, when the position of the sun is changed or when the surrounding light is turned on or off, the captured image will change very significantly. Such factors prevent the accuracy of a general face recognition system from being improved.